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Breast Tomosynthesis

Authors: Dr Kirti Mehta * Dr Felicity Pool *

What is breast tomosynthesis?

Although mammography is recognised as a reliable test for detecting breast cancer, it does have limitations. In particular, for women with dense breast tissue, small breast cancers can be missed due to masking by the overlying tissue. False positives can also result due to tissue overlapping giving composite or summation density leading to normal tissue appearing as abnormal, resulting in the need for further testing.1

Breast tomosynthesis (3D mammography) is a newer advanced technology that has been designed to overcome the limitations and challenges associated with conventional 2D mammography by reducing tissue overlap leading to an increase in sensitivity and specificity of breast cancer detection.2,3

Numerous clinical studies have shown that adding breast tomosynthesis to a diagnostic mammogram increases the breast cancer detection rate. It decreases the need for additional mammographic work up and the patient recall to breast screen assessment clinics, thus reducing the number of false positive cases.2,4,5,6,7

The breast tomosynthesis examination uses low-dose X-rays, and can be carried out as a part of a diagnostic study at the same time as the 2D mammogram. It does, however, require newer and specialised equipment. During a breast tomosynthesis examination, the X-ray arm sweeps in an arc over the breast. Images are taken at varying angles, and the images are then reconstructed using a computer into thin slices of 3D volume for review by the radiologist. The thin slices allow the radiologist to view the structures of the breast layer by layer, eliminating the effects of overlapping of the breast tissue.

Breast tomosynthesis allows better visualisation and characterization of masses, asymmetric densities, and areas of true architectural distortions in the breast leading to a reduction in the number of biopsies required.8,9

At the current level of technology and use, tomosynthesis is not recommended for the assessment of microcalcifications. These are more clearly visible using standard 2D images.

What are the generally accepted indications for a breast tomosynthesis?

Breast tomosynthesis (3D mammography) is not yet approved, and has limited availability as part of the Australian screening program through BreastScreen Australia.10 However, it is available in some private and public health breast imaging services as an accepted adjunct to the standard diagnostic mammogram.

In addition to the established indications for diagnostic mammography (see Diagnostic Mammography), breast tomosynthesis might be of particular benefit in:

symptomatic high-risk patients;

symptomatic patients where diagnostic mammography is normal or equivocal; and

those patients with dense breasts (common in women under the age of 50 years).1,2

What are the prerequisites for having breast tomosynthesis done?

Breast tomosynthesis (3D mammography) should be carried out after diagnostic mammography when the radiologist feels that tomosynthesis could provide additional valuable diagnostic information.

What are the absolute contraindications for breast tomosynthesis?

There are no absolute contraindications for breast tomosynthesis.

What are the relative contraindications for breast tomosynthesis?

These are generally the same as diagnostic mammography.

Low-risk patients under the age of 30 years. Unless the patient is considered a ‘high risk’ category, then tomosynthesis is rarely carried out in young women, because of the density and radiation sensitivity of the breast tissue.

Pregnancy and breastfeeding. Breast changes during pregnancy and lactation are usually due to benign causes; however, breast cancer can present during this time, and it is important that diagnosis is not delayed or compromised. Ultrasound is the breast imaging examination of choice for pregnant and lactating women presenting with symptoms. This is due to a greater breast density degrading mammogram images, the need to minimise foetal radiation exposure, and concerns that proliferating pregnant and lactating breast tissue could possibly be more than usually sensitive to radiation11. If suspicious findings are present clinically, on ultrasound and/or on biopsy, then mammography to assess the extent of disease can be carried out, with additional radiation shielding of the pregnant abdomen. Routine screening 2D or 3D mammography can generally be deferred until after weaning, when breasts are likely to be less dense.

Assessment of microcalcifications. Tomosynthesis is currently not recommended for diagnostic interpretation of microcalcifications. This is due to technical and perceptual difficulties in analysis. Standard 2D mammography remains the investigation of choice.

What are the adverse effects of breast tomosynthesis?

Immediate

Very occasionally, bruising or splitting of the skin occurs. Breast implant rupture has been reported; however, the risk is very low. Care is taken in the degree of compression in patients with breast implants to avoid rupture.

Delayed

There is a slight increase in radiation dose when tomosynthesis follows routine diagnostic 2D imaging. However, the total X-ray dose is still small, and the risk of developing radiation-induced breast cancer from mammography including tomosynthesis remains very low.12,13

The Health Protection Agency of the United Kingdom estimates the risk of an additional cancer in a lifetime from a single mammographic examination to be in the low-risk range: 1 in 10,000 to 1 in 100,000.15 This is the same risk of developing a cancer as that which arises from exposure to the natural background radiation accumulated from the normal environment in one year.

Is there any specific post procedural care required following a breast tomosynthesis?

There is no specific post procedural care required.

Are there alternative imaging tests, interventions or surgical procedures to breast tomosynthesis?

2D mammography is recognised as the best screening test for early breast cancer, and breast tomosynthesis test has additional diagnostic accuracy. It is important to note that mammography does not detect all breast cancers, even when the cancer has caused a lump that can be felt.

In such a circumstance, a normal mammogram or breast tomosynthesis (3D mammography) examination does not mean that the lump can be ignored. In this situation, other diagnostic tests, such as breast ultrasound or breast MRI and/or a procedure, such as fine needle aspiration (FNA) or needle core biopsy, might be necessary to find out the cause of the lump. For high-risk asymptomatic patients breast MRI is the investigation of choice.

NHS Public Health England, NHS Breast Screening Programme: current position on use of tomosynthesis, March 2016, https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/517840/BSP_position_on_tomosynthesis.pdf

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